Platinum Metals Review - Volume 42, Issue 2, 1998

In the first part of this paper, published in the January issue, development work resulting in the first noble metal/oxide coated titanium electrode was described and some of the teething problems encountered were discussed. Here, the story is continued with the further development of paint compositions: platinum-only and platinum/iridium, for coating the electrodes, and their utilisation in chlorate, mercury- and diaphragm-type chlor-alkali cells. Later, these coatings were replaced by ones containing ruthenium dioxide. This part begins with the early platinum paint compositions.

Interest is growing in using polymeric electrode materials containing platinum group metals complexes in molecular electrochemistry. Here, the synthesis of functionalised polypyrrole film electrodes, formed by the oxidative electropolymerisation of pyrrole-substituted rhodium, iridium and palladium complexes is reviewed, and recent results are presented concerning the electrocatalytic reduction of protons and the hydrogenation of unsaturated organic substrates in aqueous electrolyte. Metal hydride intermediates and their involvement in reactions at the electrodes are considered, as are preliminary results of asymmetric electrosynthesis on a molecular electrode material.

Photochemical reactions of platinum metals complexes are of great importance in contributing to the understanding of the chemical reactivity and catalytic properties of platinum metals catalysts. This paper reviews some new aspects of this photochemistry and discusses potential applications in synthesising novel complexes and in exploiting platinum metals-containing catalysts. Among aspects examined are recent trends in the photochemistry of co-ordination compounds, particularly photointramolecular rearrangements, photoredox elimination and addition reactions, and the photoredox reactions of polynuclear complexes.